U.S. officials were similarly surprised last month when an Iranian admiral threatened to send naval ships to patrol off U.S. waters.

“To my mind, it reeks of desperation,” said Matthew Levitt, a former deputy assistant treasury secretary for intelligence and analysis. “It suggests to me that they are feeling cornered.”

To others, the very rashness of the alleged assassination plot raised doubts about whether Iran’s normally cautious ruling clerics supported or even know about it. Robert Baer, a former CIA case officer in the Middle East and author of several books on Iran, said there was “sloppiness about the case that defies belief.”

“Maybe things have really fallen apart in Tehran, or maybe there’s a radical group that wants to stir up the pot,” Baer said. “But the Quds are better than this. If they wanted to come after you, you’d be dead already.”